78 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
enormously, so that the percentage of water falls to 88 and below. 
But the growth is due chiefly to imbibed water. 
Now what light do these results throw upon the process of 
development ? As we have seen, development consists of the growth 
of the organism as a whole and the differentiation of its parts. But 
one important factor out of the many which are to be found in 
differentiation is the unequal growth of the different parts of the 
body. This is -very clearly seen in the development of the frog. 
Fig. 4. Curves of growth of Phaseolus multiilorus (continuous line) and Vicia faba 
(broken line). The ordinates represent actual lengths attained on the respective days 
by a bit of stem originally 1 mm. long. After Sachs, Lectures on Plant Physiology. 
